From the point of view of the US, WWII was a good war. Thinking beyond our own economy, why was this true?

There are at
least two reasons, other than those having to do with the economy, that WWII was
"good" for the US.

First, the war made the United States the
undisputed leader of the "free world."  This was, of course, partly due to economics. 
But it was also due to the fact that the US was the sole remaining major power other than the
Soviet Union.  Countries that feared communist...